1. Field of the Invention
The invention relates to circuit testing, and more particularly to a circuit testing apparatus for testing a liquid crystal display (LCD) driver.
2. Description of the Related Art
To assure quality of integrated circuits (IC), each IC is tested when manufactured. The manufacturer determines whether an IC is qualified according to a testing result for the IC and whether the IC can be supplied to manufacturers.
General IC testing is achieved using a logic tester. The logic tester can only compare the variation of high level with low level of output voltages of an IC for a pattern function. When an IC providing multiple output voltages is used, for example, an LCD driver, multiple output voltages cannot be tested, such that the IC cannot be tested. Thus, when an LCD driver is tested, a special logic tester for the LCD driver is used for testing.
FIG. 1 is a schematic view of an LCD driver comprising four output voltages. Referring to FIG. 1, an IC under test is a driving circuit of an LCD device, comprising four different output voltages V1, V2, V3, and Vss. Thus, if a pattern function test is implemented to the driving circuit of the LCD, the pattern function must be activated to enable an output pin to output the voltages V1, V2, V3, and Vss, and the driving circuit of the LCD device is measured using the special logic tester, thus determining the function of the driving circuit of the LCD device according to the measuring result and completing the test.
The special tester, which can measure multiple voltage levels at a time, for the driving circuit of the LCD device is different from a general logic tester that can measure multiple output voltages provided by a driving circuit of an LCD device. Testing the driving circuit of the LCD device is completely based on a pass or fail determination of measuring voltages.
A special signal tester for a driving circuit of an LCD device commercially sold costs millions of dollars, such that a test for a special signal tester for a driving circuit of an LCD costs is relatively high, while a cheaper general logic tester cannot achieve required testing. Thus, an improved circuit testing apparatus is desirable.